1. Field of the Invention
This invention generally relates to a multi-disk clutch used in a transmission of a vehicle or the like. More specifically, the present invention relates to a multi-disk clutch provided with a core plate to which a friction member is joined.
2. Background Information
Generally, a multi-disk clutch is typically used in an automatic transmission of a vehicle or the like. The multi-disk clutch is usually provided with a plurality of input friction plates and a plurality of output friction plates. The input and output friction plates are alternately arranged relative to each other. The multi-disk clutch is also provided with input and output cylindrical members, which are arranged radially inside and outside the input and output friction plates, respectively. Each of the input and output friction members is provided at its inner or outer periphery with teeth, which are axially movably engaged with grooves formed on the cylindrical member located radially inside or outside the friction plate.
A transmission provided with the multi-disk clutch of the above type is disclosed in Japanese Laid-Open Patent Publication No. 10-252777. As seen in FIG. 12 of this application, a partial cross-sectional view of a multi-disk clutch 6 is illustrated corresponding to the multi-disk disclosed in the aforementioned publication. The transmission disclosed therein is provided with a pair of multi-disk clutches with only the second multi-disk clutch 6 being shown in FIG. 12.
The prior art multi-disk clutch 6 forms a brake, which is provided with two kinds of friction plates, i.e., three first friction plates 50 and two second friction plates 51 disposed alternately thereto. Each first friction plate 50 has radially outer teeth, which are engaged to move in an axial direction (i.e., movably in a direction of an axis Oxe2x80x94O) but non-rotatably coupled with grooves formed on an inner periphery of a radially outer cylindrical wall 52. Each second friction plate 51 has radially inner teeth. The teeth of the second friction plates 51 are engaged with grooves that are formed on an outer periphery of a cylindrical portion 69 of a spline hub. This is done so that the second friction plate 51 moves in an axial direction (i.e., movably along the axis Oxe2x80x94O) but is non-rotatably coupled to the cylindrical portion 69 of the spline hub. stop plate 53 is arranged to support a surface of the first friction plate 50 on the right end that is remote from the second friction plate 51. The stop plate 53 has a radially outer portion, which is fitted and fixedly coupled to a groove formed on the inner periphery of the radially outer wall 52. A piston plate 55 is opposed to a surface of the first friction plate 50 on the left end that is remote from the second friction plate 51. The piston plate 55 is slidably engaged with grooves on the inner periphery of the radially outer wall 52. In this structure, the multi-disk clutch 6 is engaged when the piston plate 55 is hydraulically moved rightward, and is disengaged when the piston plate 55 moves leftward.
In a conventional multi-disk clutch, a core plate to which a friction member is joined has a relatively large thickness, as can be demonstrated by the aforementioned multi-disk clutch 6 disclosed in the above-mentioned publication. For example, in the multi-disk clutch 6 shown in FIG. 12, a core plate 51b supporting friction members 51a joined thereto has a thickness in a range from about 1.0 mm to about 1.5 mm. This is because the radially inner teeth of the second friction plate 51 (i.e., the radially inner teeth of the core plate 51b) mesh with the grooves on the cylindrical portion 69. Thus, the teeth must have a tooth surface equal to or greater than a predetermined area to ensure a sufficient torque transmission capacity. In other words, the thickness of the core plate 51b is determined based on the area of the tooth surface required for the torque transmission.
However, it is also desirable to reduce the overall thickness (L1 shown in FIG. 12) of the multi-disk clutch, so that the size of the transmission can be reduced. This allows the transmission to be installed in an area where the available space is limited.
In view of the above, there exists a need for multi-disk clutch and method of manufacturing a core plate of a multi-disk clutch which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the invention is to reduce the thickness of a multi-disk clutch, and thereby reduce the size of a device such as a transmission provided with the multi-disk clutch.
According to one aspect of the present invention, a multi-disk clutch for transmitting and interrupting a torque between first and second members includes a plurality of first plates and a plurality of second plates. Each of the first plates is circumferentially coupled to the first member. Each of the second plates has a core plate and a friction member. The core plate has a friction mounting portion and a coupling portion. The friction mounting portion is opposed to the first plate. The coupling portion is circumferentially coupled to the second member. The friction member is joined to the friction mounting portion of the core plate. The friction mounting portion of the core plate has a thickness smaller than a thickness of the coupling portion of the core plate.
According to the multi-disk clutch of the above aspect of the present invention, the friction member which is joined to the friction mounting portion of the core plate is opposed to the first plate. When the friction member is pressed to the first plate, the multi-disk clutch enters the coupled state to transmit the torque between the first and second members. When a force for the above pressing is released, the multi-disk clutch assumes the released state to interrupt the torque transmission between the first and second members.
In the above aspect of the present invention, the coupling portion of the core plate reliably has a thickness required for the intended torque transmission. Further, the friction mounting portion of the core plate joined to the friction member has a smaller thickness than the coupling portion. More specifically, the multi-disk clutch is configured to suppress an increase in thickness of the friction mounting portion, while maintaining a large thickness for the coupling portion, which is not joined to the friction member. The friction mounting portion supports the friction member joined thereto and is liable to increase the whole thickness of the multi-disk clutch. Thereby, the same torque transmission capacity as that in the prior art can be ensured. Further, the portion (i.e., friction mounting portion) of the core plate joined to the friction member has a smaller thickness than in the prior art. Therefore, the thickness of the multi-disk clutch is reduced as a whole, and a device employing this multi-disk clutch can be reduced in size.
According to the another aspect of the present invention, the multi-disk clutch of the previous aspect of the present invention has a feature such that the coupling portion of the core plate and the second member mesh teeth for coupling the coupling portion of the core plate to the second member. In this aspect of the present invention, the coupling portion of the core plate and the second member are coupled via the meshing structure. The core plate has the friction mounting portion with small thickness as well as the coupling portion with large thickness. Thus, teeth meshing with the second member can reliably have a sufficiently large tooth surface area, and a sufficient torque transmission capacity can be ensured.
According to another aspect of the present invention, the multi-disk clutch of any of the previous aspects of the present invention, further has a feature such that the coupling portion of the core plate and the second member are coupled together via an internally-toothed wheel. In this aspect of the present invention, a toothed wheel provided with external teeth and the internally-toothed wheel provided with internal teeth mesh with each other for transmitting the torque between the coupling portion of the core plate and the second member. Although the friction mounting portion of the core plate has the smaller thickness, the coupling portion of the core plate has the larger thickness. Thus, the teeth of the coupling portion meshing with the second member can reliably have a sufficiently large area.
According to another aspect of the present invention, the multi-disk clutch of one of the last two mentioned aspects of the present invention further has a feature such that at least the tooth surface portion in the coupling portion of the core plate for contact with the tooth of the second member has a larger thickness than the friction mounting portion of the core plate. In this aspect of the present invention, the tooth surface portion in the coupling portion has a thickness larger than that of the friction mounting portion. The tooth surface portion can come into contact with the second member. Thereby, the area of the tooth surface required for the torque transmission is ensured while suppressing a need for an increase in overall thickness of the multi-disk clutch.
According to another aspect of the present invention, the multi-disk clutch of any one of the first three mentioned aspects of the present invention, further has a feature such that the coupling portion of the core plate projects externally beyond one side surface of the friction mounting portion of the core plate. This provides an L-shaped section of the core plate. In this aspect of the present invention, since the core plate has the L-shaped section, the core plate can be easily formed, e.g., by press work.
According to another aspect of the present invention, the multi-disk clutch of any one of the first three mentioned aspects of the present invention, further has a feature such that the friction members are joined to the opposite side surfaces of the friction mounting portion of the core plate. The coupling portion of the core plate projects externally beyond the opposite side surfaces of the friction mounting portion so that the core plate has a T-shaped section. In this aspect of the present invention, since the core plate has the T-shaped section, required thickness of the coupling portion of the core plate can be ensured more easily than in the case of the L-shaped section.
According to another aspect of the present invention, a method of manufacturing a core plate having an integral structure of the multi-disk clutch of any one of the previous aspects of the present invention, includes a first step and a second step. In the first step, a material member having a thickness equal to that of the friction mounting portion, and having a larger area than that of the plane area of the core plate of a final configuration is prepared. In the second step, a force is applied to the material prepared in the first step in a direction crossing the direction of its thickness, and thereby increasing the thickness of a portion forming the coupling portion. In this aspect of the present invention, the second step is executed on the plate-shaped material having the uniform thickness for increasing the thickness of the coupling portion. For example, pressing is effected to apply the force in the direction, which is substantially perpendicular to the direction of the thickness of the material, while pushing the end surface and/or upper and lower surfaces of the material. Thereby, the core plate of an integral structure, in which the coupling portion has the increased thickness, can be formed from the plate-shaped material.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.